Field of the Invention
The invention relates to optoelectronic semiconductor components. More particularly, the invention pertains to a method for producing an optoelectronic semiconductor component, specifically for applications having very narrow radiation and/or reception characteristics. The components comprise a chip carrier, which has an approximately planar chip carrier surface and on which an optoelectronic semiconductor chip is fastened with predetermined alignment of its optical axis, and a base part, which is assigned to the chip carrier, supports the latter and is produced from a plastic material, the semiconductor chip being electrically conductively connected to at least two electrode terminals routed through the base part, and the semiconductor chip being assigned a lens, which covers over the base part.
Prior art optoelectronic semiconductor components, in particular those which are subject to increased demands with regard to their optical properties, have largely been produced in metal-glass housings. There, the chip carriers are, usually, baseplates produced from metal mounted with a metal cap with a glass lens fitted in. Due to the mounting by means of a metal housing, it has been possible, on the one hand, to ensure a hermetically sealed closure of the housing and, on the other hand, to provide suitability of the optoelectronic semiconductor component for specific high-temperature applications starting from about 150.degree. C. The ageing of the semiconductor chip given such a type of mounting was slight since, on account of the metal housing type used, there was essentially no loading on the semiconductor chip on account of directly surrounding material. Finally, it has been possible to configure the optical properties of the semiconductor component favorably on account of the glass lens fitted into the metal cap.
The considerable costs necessarily incurred by the relatively complicated production are regarded as a significant disadvantage of the optoelectronic semiconductor components that have been produced to date. In this case, the metal cap with a glass lens fitted in, which requires a high production outlay, has a particular impact. Furthermore, the semiconductor components mounted in metal-glass housings have problems on account of the adjustment and manufacturing tolerances that must be estimated to be relatively large, with the result that such optoelectronic semiconductor components generally have relatively unfavorable squint angles. These are production-dictated deviations of the optical axis from the mechanical axis of the component. As a result, such semiconductor components can only be used to a limited extent in applications which involve narrow radiation and/or reception characteristics. In the prior art optoelectronic semiconductor components, a larger adjustment play during mounting consequently has an extremely unfavorable effect on the squint angle obtained, given closer tolerance specifications.
Furthermore, mass-produced plastic light-emitting diodes having lesser requirements with regard to the optical qualities are known in which the housing with a baseplate and a cap is cast in one process operation and thus produced in one part. That production process is significantly less expensive than metal-glass housings. However, as a result of the single work operation of the (pressureless) casting production, excessively high adjustment tolerances and thus high squint angles are produced. The optoelectronic semiconductor components produced in such a way have quite unsatisfactory optical properties for specific applications.
There have become known, as disclosed in Patent Abstracts of Japan, Vol. 16, No. 055 (E-1165), Feb. 12, 1992, & JP-A-03254162, a light-emitting diode with a base part made of metal and a plastic cap with a lens part. There, the object is to improve the positioning accuracy and to increase the emission rate.
Reference is also had to Patent Abstracts of Japan, Vol. 11, No. 367 (E-561), Nov. 28, 1987 & JP-A-62139367 and Patent Abstracts of Japan, Vol. 11, No. 312 (E-548), Oct. 12, 1987 & JP-A-62105486, which show further light-emitting diodes with separately configured lens caps.